Thermodynamic stability of chemically delithiated Li(Li{sub x}Mn{sub 2{minus}x})O{sub 4}
- Simon Fraser Univ., Burnaby, British Columbia (Canada). Dept. of Physics
- Dalhousie Univ., Halifax, Nova Scotia (Canada). Dept. of Physics
Stoichiometric and excess-lithium spinels, Li(Li{sub x}Mn{sub 2{minus}x})O{sub 4} (x = 0.0, 0.1, 0.2), were treated with diluted H{sub 2}SO{sub 4}. The resulting products retained the spinel structure at reduced lithium content; those with lowest lithium content underwent exothermic phase transitions, observed as peaks in differential scanning calorimetry (DSC) curves between 250 and 300 C at heating rates of 10 C/m. The phase transition of the delithiated stoichiometric spinel was followed by powder X-ray diffraction of heat-treated samples. The structural analysis shows that the oxygen atoms rearrange first (from cubic to hexagonal packing), leaving the manganese atoms in disordered positions. It is this rearrangement of oxygen atoms that releases most of the heat observed in DSC measurements. Eventually the manganese atoms took their expected positions in the rutile or {beta}-form of MnO{sub 2}. The metastability of the delithiated compounds turned out not to be the origin of the capacity fade in electrochemical cells using stoichiometric spinel as the cathode.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 599914
- Journal Information:
- Journal of the Electrochemical Society, Vol. 145, Issue 2; Other Information: PBD: Feb 1998
- Country of Publication:
- United States
- Language:
- English
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